Multipolar endocardial mapping of the right heart using a basket catheter: acute and chronic animal studies

Basket-Type Catheters: Diagnostic Pitfalls Caused by Deformation and Limited Coverage

Whole-chamber mapping using a 64-pole basket catheter (BC) has become a featured approach for the analysis of excitation patterns during atrial fibrillation. A flexible catheter design avoids perforation but may lead to spline bunching and influence coverage. We aim to quantify the catheter deformation and endocardial coverage in clinical situations and study the effect of catheter size and electrode arrangement using an in silico basket model. Atrial coverage and spline separation were evaluated quantitatively in an ensemble of clinical measurements. A computational model of the BC was implemented including an algorithm to adapt its shape to the atrial anatomy. Two clinically relevant mapping positions in each atrium were assessed in both clinical and simulated data. The simulation environment allowed varying both BC size and electrode arrangement. Results showed that interspline distances of more than 20 mm are common, leading to a coverage of less than 50% of the left atrial (LA) surface. In an ideal in silico scenario with variable catheter designs, a maximum coverage of 65% could be reached. As spline bunching and insufficient coverage can hardly be avoided, this has to be taken into account for interpretation of excitation patterns and development of new panoramic mapping techniques.

Imaging and visualization of 3-D cardiac electric activity

Noninvasive imaging of cardiac electric activity is of importance for better understanding the underlying mechanisms and for aiding clinical diagnosis and intervention of cardiac abnormalities. We propose to image the three-dimensional (3-D) cardiac bioelectric source distribution from body-surface electrocardiograms. Cardiac electrical sources were modeled by a current dipole distribution throughout the entire myocardium, and estimated by using the Laplacian weighted minimum norm (LWMN) algorithm from body-surface potentials. The estimated inverse solution of the current distribution was further improved by using a recursive weighting strategy for localized sources, such as origins of cardiac arrhythmias. Computer simulations were conducted to test the feasibility of the proposed approach by using a 3-D ventricle model embedded in a realistically shaped torso model. The boundary element method was used to solve the forward problem from assumed cardiac sources to the body-surface potentials. Two testing dipoles were placed in the left and right ventricles, simulating the early activation associated with ventricular arrhythmias. The LWMN inverse solution showed an equivalent source distribution over the entity of both ventricles, with spread areas of activity overlying the positions of the testing dipoles. The sharpened inverse image provides well-localized focal sources near the testing dipole positions. In summary, the present computer simulation suggests that the proposed 3-D cardiac current source imaging and localization approach appears to be a promising candidate for localizing and imaging sites of origins of cardiac activation.

Automated classification of human atrial fibrillation from intraatrial electrograms

The assessment of the degree of organization and the classification of atrial fibrillation (AF) according to the types defined by Wells usually resorts to the visual inspection of bipolar intraatrial electrograms. The focus of this study was to test seven parameters aimed to quantify the degree of organization of the electrograms, and then to design a final classification scheme based on a multidimensional, minimum-distance analysis. The following parameters were tested: mean atrial period (AP) and its coefficient of variation (CV); number of points lying at the baseline (NO) and the Shannon entropy (EN) of the amplitude probability density function (APDF); depolarization width (F-WIDTH); and correlation waveform analysis (CWA) and electrogram bandwidth (BW). The signal database consisted in a set of 160 AF strips of Type I, II, and III AF, scored by an expert cardiologist (60 Type I, 40 Type II, 60 Type III) and further divided in a training set (60) and a test set (100). Strips were 6 seconds long and were recorded with 5-mm interspace bipolar catheters from electrically induced (n = 13) and chronic (n = 10) patients. A classification algorithm based on a minimum-distance (Mahalanobis distance) discriminant analysis was tested. Using a single parameter, the best discriminations were provided by NO, F-WIDTH, and CV. F-WIDTH was found strongly inversely correlated to NO (r = -0.90). Of all the two-parameter combinations, CV-NO provided the best classification: 92 of 100 segments were correctly classified with sensitivity > 90% and specificity > 92%. A further improvement was obtained by including BW as a third parameter (93/100 correctly classified). The use of more than three parameters not only failed to improve, but even degraded the classification.

Acute animal studies of the STARFlex system: a new self-centering cardioSEAL septal occluder

The STARFlex system is a modified CardioSEAL device with a flexible self-centering mechanism comprised of nitinol springs strung between opposing arms, a connecting ball (sleeve joint that allows the device to pivot prerelease), and a front-loading delivery system. It was designed to allow a smaller device/defect sizing ratio and delivery profile, provide centering capability, and improve closure rates. To test this system, 13 devices (23, 28, and 33 mm) were deployed in six sheep within created atrial septal defects (12- to 22-mm diameter; n = 10), in the left atrium (n = 2), and in inferior vena cava (n = 1). All implantations in atrial septal defects were successful, with device/defect ratio ranging from 1.3 to 1.9 (median, 1.3), with no residual leak by angiography or echocardiography in seven (3/10 had </= small immediate leaks). The STARFlex system was effective in closing created atrial septal defects using a 10 Fr delivery sheath and low device/defect sizing ratios, comparing favorably with the standard CardioSEAL. Cathet. Cardiovasc. Intervent. 49:225-233, 2000.

Basket catheter localization of the origin of atrial tachycardia with atypical morphology after atrial flutter ablation

Atrial activation from a site in the low lateral right atrium will typically proceed in a superior direction. We present a case of a low lateral right atrial tachycardia with a surface electrocardiographic P wave morphology that appeared to have an inferiorly directed axis. The tachycardia occurred 2 years after successful atrial flutter ablation. The use of a multipolar basket catheter allowed confirmation of the focal origin of the tachycardia, permitted its rapid localization, facilitated catheter ablation, and provided clues to atrial activation that helped describe the appearance of the P wave.

Clinical experience with a novel multielectrode basket catheter in right atrial tachycardias

BACKGROUND

The complexity of atrial tachycardias (ATs) makes the electroanatomic characterization of the arrhythmogenic substrate difficult with conventional mapping techniques. The aim of our study was to evaluate possible advantages of a novel multielectrode basket catheter (MBC) in patients with AT.

METHODS AND RESULTS

In 31 patients with AT, an MBC composed of 64 electrodes was deployed in the right atrium (RA). The possibility of deployment, spatial relations between MBC and RA, MBC recording and pacing capabilities, mapping performance, and MBC-guided ablation were assessed. MBC deployment was possible in all 31 patients. The MBC was left in the RA for 175+/-44 minutes. Stable bipolar electrograms were recorded in 88+/-4% of electrodes. Pacing from bipoles was possible in 64+/-5% of electrode pairs. The earliest activity intervals, in relation to P-wave onset, measured from the MBC and standard roving catheters were 41+/-9 and 46+/-6 ms, respectively (P=0.21). Radiofrequency ablation was successful in 15 (94%) of 16 patients in whom it was attempted, including 2 patients with polymorphic right atrial tachycardia (RAT), 2 with RAT-atrial flutter combination, 1 with macroreentrant AT, and 1 with focal origin of atrial fibrillation.

CONCLUSIONS

These data demonstrate that MBC can be used safely in patients with right atrial arrhythmias. The simultaneous multielectrode mapping aids in the rapid identification of sites of origin of the AT and facilitates radiofrequency ablation procedures. The technique is especially effective for complex atrial arrhythmias.

Electroanatomic imaging using magnetic catheter tracking in the diagnosis and treatment of atrial arrhythmias

Recent data emphasize the importance of structural factors in the pathophysiology of atrial arrhythmias. As a consequence, catheter ablation increasingly has become an anatomically oriented procedure. A recently developed magnetic catheter tracking system provides spatially precise and realistic three-dimensional reconstructions of endocardial geometry. A variety of electrophysiologic data can be superimposed on these reconstructions, including activation sequence, electrogram amplitude and morphologic features, response to pacing maneuvers, and sites of planned or delivered radiofrequency energy ablation. These features enhance the ability to analyze and visualize arrhythmia mechanisms, plan and execute appropriate ablation strategies, and provide new opportunities for physiologic research.

Type I atrial flutter ablation guided by a basket catheter

Bidirectional isthmus conduction block has been associated with a low recurrence rate after atrial flutter ablation. We present the case of a type I, typical or "counterclockwise" atrial flutter ablation guided by stimulation and recordings obtained from a basket catheter, which allowed for constant electrogram recording from splines positioned along the right lateral free wall and septum. After atrial flutter termination with radiofrequency application, the ability to record and stimulate from multiple sites in the atrium using the basket catheter was useful to detect residual bidirectional slow conduction through the isthmus. Complete isthmus block could be documented after additional radiofrequency energy applications.